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Two Orbits valves on one air chamber: fratricide?

Post questions and info about pneumatic (compressed gas) powered cannons here. This includes discussion about valves, pipe types, compressors, alternate gas setups, and anything else relevant.
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Two Orbits valves on one air chamber: fratricide?

Unread postAuthor: WingerCT » Wed Sep 28, 2011 10:17 pm

Hi all-

New poster here, and I really believe I have tried to answer this question via the search function, so please be gentle with me.

I learned two things from that unfruitful approach:
1) This place is frikkin huge.
2) There are an awful lot of brilliant but clearly psychotic engineers out there with far too much free, unsupervised time available. I may not leave home tomorrow for fear that an unexpectedly successful project by one of you puts a high-velocity cabbage through my forehead. From six miles away.

My humble question relates to the internal durability of the revered and abused Orbits 57461 sprinkler valve.

I have a project in mind that would involve two of these valves sharing an air chamber for what is effectively a double-barrelled nerf rocket launcher.

Imagine two of these valves at opposite ends of a shared air chamber. Perhaps at 100psi, The valves are outputting to two separate barrels.

I fire one barrel, mercilessly attacking my enemy. Insert evil chortle here.

What happens to the diaphragm and firing mechanism of the *other* valve, which now has it's intake side pressure violently dropped to 0 psi? How does the pilot area behave?

The chamber refills immediately from a regulated on-board air source, but did I just blow out a diaphragm? Or launch the other missile at a nearby referee? Or have a childish accident? Perhaps all three, which will make a great story someday?

If any of you successfully visualize my problem, A) good on you, and B) you clearly have worked with the mentally handicapped in the past. Good on you, too.

Thanks for any insights. If this has been discussed elsewhere around here, feel free to point me there and we can all move on to more fruitful topics like pumpkin chucking.

-Winger
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Unread postAuthor: Technician1002 » Wed Sep 28, 2011 11:45 pm

You have my admiration for understanding the valves and anticipating a possible problem. With a very small chamber, the rapid loss of chamber pressure may cause damage. With a larger chamber and the finite rate the chamber pressure will drop, the possibility exists that the EQ hole will be big enough to prevent too high of a pressure differential on the diaphragm. For evidence of the survivability in this configuration, it would pay to look for examples where others have tried it.

I won't look it up now, but there were a few commercial confetti cannons that used 2 barrels with two valves on one tank. They could be fired sequentially or in tandem.

I am not sure how well your valves will survive with your chamber size. A possible timing circuit to limit your valve dwell time could possibly re-close the valve before the chamber pressure reaches 0 which could both preserve the valve and possibly permit a rapid dual barrel shot.
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Re: Two Orbits valves on one air chamber: fratricide?

Unread postAuthor: jackssmirkingrevenge » Wed Sep 28, 2011 11:47 pm

WingerCT wrote:I learned two things from that unfruitful approach:
1) This place is frikkin huge.
2) There are an awful lot of brilliant but clearly psychotic engineers out there with far too much free, unsupervised time available. I may not leave home tomorrow for fear that an unexpectedly successful project by one of you puts a high-velocity cabbage through my forehead. From six miles away.


That is possibly the most accurate assesment of this forum I've ever read :)

Also this:

Two Orbits valves on one air chamber


... sounds like a spudder's porn flick directed by POLAND_SPUD :D

As to your question, I don't believe it's ever been attempted as dual sprinkler valves mounted on the same chamber are usually fired simultaneously so I can't think of any physical example to point you to.

Image

Looking at the construction of a sprinkler valve though, it seems unlikely that the diaphragm will rupture, especially as the pilot area will ultimately leak back into the chamber so the stress is only momentary.

It does beg the question though, why two valves on one chamber if you intend to fire them separately? There seem to be many other less unconventional ways of getting two shots in sequence, what exactly is the effect you're after?
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Re: Two Orbits valves on one air chamber: fratricide?

Unread postAuthor: PVC Arsenal 17 » Wed Sep 28, 2011 11:57 pm

jackssmirkingrevenge wrote:It does beg the question though, why two valves on one chamber if you intend to fire them separately? There seem to be many other less unconventional ways of getting two shots in sequence, what exactly is the effect you're after?


My thoughts exactly. It would be a trivial matter to divert flow from your regulated supply to one chamber or the other.

If I get around to it I'd be happy to test this out for you. The prospect of destroying components for the hell of it sounds very exciting.
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Unread postAuthor: WingerCT » Thu Sep 29, 2011 1:01 am

I already feel so at home here. This does not bode well.

It is far beyond my bedtime, and excessive crankiness in the morning tends to alarm my dog. So I will be brief:

Here is an extremely crude drawing of what I am raving about. You all should know that function is dictating form. The final result needs to be as light as possible, man-portable and weight balanced, hence the effort to have just one air chamber.

Image

I will add more tomorrow, unless some sanity returns.

("Two Orbits valves on one air chamber" My god how did I miss that opportunity to immediately alienate everyone. I must be slipping. :lol: )

Thanks very much for the helpful responses, folks.
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Unread postAuthor: jackssmirkingrevenge » Thu Sep 29, 2011 1:19 am

Are two barrels essential?

I would think that the following would be a better idea:

68 ci tank -> reg -> single 3/4" Quick Exhaust Valve with slide valve pilot -> single CO<sub>2</sub> tank as chamber.

This will give you a setup that efficiently fires one shot per trigger pull, shutting off the main air supply in the same step and only dumping whatever the CO<sub>2</sub> tank contains.

This assumes it's not important to have electric firing, which you seem to have retained in your original plan with no indication that sprinkler valves would be modded for manual piloting.

You can then have two (or more ;)) barrels rotating on a common axis, and simply flip them round for each shot.

Less cumbersome would be a simple hole cut into the breech of your barrel, covered with a tight fitting sleeve, et voila, "bolt action".

Some indication of what sort of performance you're after (type and weight of projectile to what velocity) would also be useful in order to determine what parameters you should be looking for.
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Unread postAuthor: Crna Legija » Thu Sep 29, 2011 1:40 am

Doubt it will break they have a pretty sturdy plastic washer inside that would stop it from popping fro pilot pressure.

Still don't get why you would have two barrels and one chamber, if its because of reload time, just make a sleeve over a single barrel for a breach loader.


edit: dam, jsr do you ever sleep?
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Unread postAuthor: jackssmirkingrevenge » Thu Sep 29, 2011 2:21 am

Crna Legija wrote:jsr do you ever sleep?


4-5 hours a night and even that is punctuated by silly dreams ;)
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Unread postAuthor: Technician1002 » Thu Sep 29, 2011 7:12 am

http://www.aclassactfx.com/freeaircannon.htm

Looked up the confetti cannon I mentioned. They are not using sprinkler valves, but it does use a diaphragm valve like a sprinkler valve. They mention getting dual shots when using a short dwell time.

Image

Similar to the AE03 Electric Air Cannon above, but has an extra barrel and firing valve, so you can fire twice before reloading is necessary. Barrels should be fired separately, to have a full tank of air behind each shot. It's important to use a momentary switchbox for this cannon, because if you let all the pressure out of the tank when you fire the first barrel, there will be none left to fire the second barrel.


For them, two valves on one chamber is not a problem, but they use a huge chamber.
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Unread postAuthor: WingerCT » Thu Sep 29, 2011 11:38 am

Nice to see I've at least presented you folks with a new question. :twisted: That confetti cannon is closely related- thanks for that.

I can see why some of you are puzzled by my approach, but as I said, the device has to fit some very specific physical parameters, particularly size and weight. But there is also the all important cool factor, otherwise why do it at all? 8)

The project is to build a walking "tank" for paintball or airsoft use, but designed to look and function more like an attack helicopter. The device I drew above would have a barrel on each side of the operator at about waist height, mounted to an ALICE backpack frame via the horizontal 1/2" steel pipe component. The whole cannon rig will be easily detachable if not needed.

Short "handlebars" parallel to the tubes will protrude forward inside the "cockpit" to help the operator aim and adjust elevation, (fwiw...), and provide mounting points for the electric firing switches. (Yes, I was hoping to use electric solenoids for more flexible controls and the safety of a master arming switch. I also suspected that the odd pressure changes in the valves due to the shared chamber that I am mainly concerned about might also interfere with pneumatic triggers, even though they are more efficient.)

The two "missile launchers" would have to be about 28" apart, which when the length of two valves are factored in, limits the size of the air chamber. (I think the valves would be less likely to get broken if mounted on the back of the frame, rather than outboard behind the tubes.)

My thought was that a single shared ~110ci chamber would give each launcher adequate performance at 50-100psi with barrels between 12-18" long, even though they could not fire simultaneously. (Which is fine, although the dwell delay is an intriguing idea.)

Overall weight is a big issue as well, and I thought one 110ci tank with fittings is lighter and allows lower operating pressure than two separate 55ci ones with separate fittings. (Thank you GGDT!) The two CO2 (air) chambers would be angled back and up both for safety and as a counterweight to the barrels. The exact barrel length would depend on the final proportions when worn- the plan is that these would be muzzle loaded, so lighter shorter tubes the operator can reach in front of are preferable.

I think. :?

Look, you people are the smarty pantses around here. I've never done this before, and am mildly astonished I am doing it now. I'm generally a very sedate, polite, upstanding fellow. Other than the whole pole dancing thing, which is getting a little old anyway. As am I, so I am told.

So should I go ahead and order two valves, set it up, and find out which fails first: the valves or my health insurance policy? Anybody have a better approach?
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Unread postAuthor: jackssmirkingrevenge » Thu Sep 29, 2011 11:51 am

More technical commentary to follow (stuck at work trying to finish a report :s) but won't the poor fellow walking around pretending to be an attack helicopter look like a bit of a çunt, even if he's packing a big bore multi-barrel pneumatic?

Reminds me of this joke :D

A private was on the battlefield in Germany in 1945. His platoon was running out of ammo. The guy's Sergeant told him: "Private, just aim your empty rifle at the enemy and say 'bangety-bang-bang'; it's your only hope."

So the guy aimed his empty rifle at the advancing Germans and say "bangety-bang-bang"; to his shock and delight 3 Germans fell dead in their tracks. He repeated it, with the same results. Again and again.

But then disaster struck. One large determined German appeared and trudged straight ahead, not falling. "bangety-bang-bang"... the Nazi kept on trudging ahead, eyes glazed. "bangety-bang-bang"...nothing. "bangety-bang-bang"...nothing. The German was just feet in front of him, never wavering. The private threw his rifle at the enemy, but it just bounced off.

Soon the private was trod down in the mud by the advancing spectre. As the German crushed him into the ground the last thing the private heard was the German saying "clankity-clank-clank, I'm a tankity-tank-tank!"
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Last edited by jackssmirkingrevenge on Thu Sep 29, 2011 12:00 pm, edited 1 time in total.
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Unread postAuthor: WingerCT » Thu Sep 29, 2011 12:00 pm

jackssmirkingrevenge wrote:More technical commentary to follow but won't the poor fellow walking around pretending to be an attack helicopter look like a bit of a çunt, even if he's packing a big bore multi-barrel pneumatic?


Yes. That is why I will make someone else on the team climb into this deathtrap. I don't need the stress and humiliation. I have teenagers for that.

A certain suspension of disbelief is required. Roll with it. ;)

Awesome joke. Consider it stolen. :D
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Unread postAuthor: Technician1002 » Thu Sep 29, 2011 12:19 pm

Some of the claims for some of the cannons here will now make me think
"clankity-clank-clank"
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Unread postAuthor: jackssmirkingrevenge » Thu Sep 29, 2011 2:29 pm

Blackadder: If I can remind you of the realities of battle George, one of the first things everyone notices is that all the protagonists keep their clothes ON. Neither we nor the Hun favoue fighting our battles au naturel...

George: It's artistic licence Sir... it's the willing suspension of disbelief!

Blackadder: Well I'm not having anyone staring in disbelief at my willy suspension!


Seriously though, the poor sod having to hump this rig around already has enough to deal with, making him muzzle load his "rocket launchers" is a bit much.

I would put some extra effort into a loading mechanism.

Can't he have single a centreline mounted cannon instead?

One efficiently fed barrel is going to be a lot better than two clumsy side mounted barrels...
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Unread postAuthor: WingerCT » Thu Sep 29, 2011 4:19 pm

True, breech loading would be very nifty if it fits the overall ergonomics, but I figured I would burn that bridge when I came to it. For the Mark One version, muzzle loading should work alright.

A centerline mount is commonly used exactly as you suggested JSR, however the overall design I am working on (which I haven't really explained well yet), is extremely light weight, but consequently has no feasible mounting point forward of the operator for a launcher. It will just have a baffled gun port so that the operator can fire his own Paintball marker or Airsoft gun through the front of the "canopy", then withdraw it to hang from a single-point bungey sling when not in use or when deploying the rockets.

I just thought the side mounted launch tubes offered a way to shift nearly all the weight of this crazy contraption onto a balance point on the hips, so hopefully it won't be too onerous for whichever FNG I can browbeat into strapping himself into this foolish thing. We have a some big ones to pick from. :D

I guess I've missed the season to buy those valves off the shelf herabouts, so I will probably just order them from SpudTech, along with a few other handy bits like a Schrader valve and 125psi relief valve.

But I'm still mostly concerned about what will happen to the non-firing valve when it is stressed. I *think* that even if it cracks or the diaghragm fails, it would result in more of an implosion than an explosion. But I don't even know what I don't know. Is a partial vacuum created at launch that might produce a transient internal pressure beyond the valve chambers tolerances? (edit: And if the valve cracked due to implosive forces, what happens when I then try to fire that now- damaged valve? :shock: )

Maybe a layer of Kevlar on the pack frame might not be a bad idea...

Still want to blow something up, PVC Arsenal 17? :D

"...my willy suspension!" I need to rewatch those shows. :D
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